Synchrotron Microangiography of the Rat Heart Using the Langendorff Model

Background and Objectives: The ability to study microvessels of a beating heart in real time at the level of the capillary is essential for research. However, there are no proven methods currently available to achieve this. The conventional absorption-contrast agents have limitations for studying capillaries. Microangiography with using synchrotron phase-contrast X-ray technology and no contrast agent has recently been reported on. We tried to verify this previous report, and we wanted to visualize the microvessels of a rat heart using air as a contrast agent. Materials and Methods: We made the Langendorff apparatus in a hutch of the Pohang Accelerator Laboratory. The images were obtained with a white beam and a monochromatic beam. The visual images were magnified using 3× and 20× optical microscope lenses, and the images were captured with a charge-coupled device camera. Results: We could not duplicate the previously reported findings in which microvessels were visualized without the use of contrast agent. But with using air as a contrast agent, the microvasculature of rat hearts was clearly identified at a spatial resolution of 1.2 μm. Air being absorbed inside a capillary was also observed. Vessels under 10 μm diameter were unable to be visualized with using iodine as a contrast agent. Conclusion: Phase contrast imaging already allows spatial resolution of 1 μm, which is enough to inspect capillaries. We were able to obtain images of cardiac capillaries with using air as a contrast agent. Yet air has the fatal limitations in that it causes embolism and ischemia. A more suitable contrast agent or imaging method needs to be developed in order to study the microvessels of a beating heart. (Korean Circ J 2008;38:462-467)